A Secondary Saga Southbound Sextant Adventure .. "Seeking Sally"

[oldpropfan]

Read with interest Dil's info on moon phases in FS so I thought I'd take a look outside and then compare it to FSX. Must only be a couple days off because I can't really see any difference between the two, not that that's an exact measurement ( my eye calibration that is ). I was going to start using the sextant for moon shots during my first attempt at a classic era transatlantic flight so I'm glad it seems to be close to in phase.

Al

 

[salt_air]

SASA - SAME

Okay .... gave her a rip this morning after stealing some time from work ..


It's not going to be possible to match your (or anyone's) flights to the degree, minute, or NM .... same plane, same route same weather ... different pilots with different ways of managing cockpit duties and different results (slightly) in the end.

So just working in the same ball park I was able to follow to the letter everything you did technically (beautiful), but the thought process (which is what I believe most of us struggle with) still leaves me feeling like I'm on the outside looking in.

Lot's of "why" questions like a child (that I am) are generated while "going through the motions" and coupled with the slight immediacy of the flight duties themselves I find myself just skipping over them and moving on to the next task .... maybe thinking that the answer will show up down the road.




Basically, the grey area (for me now) is with the logic behind sextant based flight plans.

Part of that is with some of the other navigation methods you can play, to a certain degree, catch up and, with modern enough equipment, figure out exactly where you are.

That ability will allow you to not pay real close attention to position ... because it's just a few clicks away when you need to know.


Sextant Navigation requires a very disciplined (in comparison) acclimation to navigational duties ... pro active if you will.

A considerable amount of work with relation to flight plan is done before you even get in the cockpit or can be and to go along with what I just said .... should be.





Net so far is another notch with sextant operation and confidence with setting up and the physical action of grabbing shots.

But alas no idea of how to ask the fill in the blank questions so that I would wind up with the info I needed for the trip.




[This for average Joe who may be reading and trying to follow ... and to some extent myself as well]


Was there any particular reason for picking the time of day other than optimizing Sun angle?

I'm guessing that the aircraft's altitude is of little or no consequence?

First leg tracked out while the second tracked in to minimize the chance for error ... right?

The planned course heading (line on the map) was equal to the 0 horizontal line on the chart up until fix ... then it was equal to the vertical 0 line from there to destination ... How would average Joe know to do that?

This was a time and distance measurement exercise where the info we gathered from our sun shots equated to lines (red, green, and blue) that crossed our path (that same o line on the chart) ... yeah?

Why were shots taken at 60NM intervals again and should we always do it that way?





In this case we were using the Sextant to back up our figures we came up with by staying on course heading (as close as we could), keeping a constant ground speed (at cruise level) and keeping close eye on time and distance with the clock ... is that about it?




You nailed down the whole Moon thing very well and brought up some very interesting points on how it is rendered (or not) in MSFS.

Yeah. I knew something wasn't right between real Moon and FS Moon, but didn't have a handle on it till now ... thanks!



[BTW]

This puts me and Pedro in Mendoza ... yeah Pedro, he had to leave before the gringo's came back to find their plane broken, out of gas and a hundred miles south of where they left it ... and I needed a local guide until I get a grip on how to use the Sextant .... so things are working out for the three of us.

Me, Pedro and the ransom payment crate.





View attachment 45440View attachment 45441View attachment 45442

 

[Dil52]

Fantastic Salt_Air!!!!!

Great questions and that's great for all.

Keep them coming!!

Actually these aren 't "in the dark" questions, but rather affirmations that you got it right!......and you have!



Was there any particular reason for picking the time of day other than optimizing Sun angle?

Yes and no.

Yes, in that this was our first flight using the sun lonely. It’s important to note, that the sun’s Hc (elevation) should be at least +15° when taking readings.

((In the real world the atmosphere refracts light (distorts it.) As example we can actually see the sun, moon, and starsbefore they reach the horizon do to this refraction. That also explains why the moon looks so huge when it first comes up. The atmosphere actually stretches it. Once the sun reaches about +15 degrees the atmospheric refraction is reduced considerably. Notice how the moon gets more proportionate after it’s up for awhile)).

No, in that we don’t necessarily let the sextant determine when we’re going to fly. This flight basically only used the sun ( a single star).

Once everyone is as familiar with the sextant, as you obviously are, I believe we’ll do a flight starting at night, take some star shots, and end up in the morning daylight to locate our airport. I’d also like to do the flight ending to the Horn by starting out in the late afternoon and ending up at night.

Airports SAWH and ACGZ are only 22 miles apart and both have runway lights. ACGZ also has a beacon, which could be a great help atnight.

I’m so excited that you nailed it!

.............had to say that again!


I'm guessing that the aircraft's altitude is of little or no consequence?

Correct: The amount of bouncing you get trying to read the sextant in a airplane, with just a little turbulence, more than overrides the tiny bit of difference that compensating for altitude would have on the readings.

First leg tracked out while the second tracked in to minimize the chance for error ... right?

Correct: It was to illustrate that the coordinates we’re reading are actually our assumed position no matter which direction. When we say assumed position we’renot necessarily talking about where we are, but where the coordinates entered into the sextant are. Think of it as the exact angles to the sun from the entered coordinate. That’s why we enter the destination latitude and longitudeand and the exact time when bringing up a data chart. The difference is the reading we get.


The planned course heading (line on the map) was equal to the 0 horizontal line on the chart up until fix ... then it was equal to the vertical 0 line from there to destination ... How would average Joe know to do that?

It just worked out that way. I’ll try to explain a couple different ways.

1. When we started out, early in the morning, the Zn (azimuth) of the sun was more an eastern direction than north of us (ENE you could say in this case). The more (east or west) a star is, in relation to our ASSUMED POSSITION (reading location), the better the longitude accuracy. So, on this flight, when the azimuth of the sun was between 90° and 45° our longitudinal readings were (better) than latitude. As we flew and the sun approached noon (Zn=0°) between45° and 0° our readings became (better) latitudinal wise.

2. It is also easiy to determined by the looking at the plotted lines on the graph as well. If you noticed the readings taken early in my demo flights you can see that the lines were more vertical earlier thus the longitude distance is better. As the flight progressed, and the lines became more horizontal, the latitude distance readings were more accurate. If we had flown until high noon, the resultant reading line would have been flat and been a pure latitude only reading.

NOTE: Once you have the relationship between the data charts an the graph, firmly planted in your mind, all of a sudden you'll see how easy this is!
The Zn (azimuth) we set into the sextant is the verticle and horizontal (angle) of one particular reading (blue, green, red) line.
The Hc (elevation) we set into the sextant gives us the distance to/from the coordinates set into the sextant.

Hmmmm?

It has suddenly dawned on me that the angle of the line on the graph is also the (trueheading LOP not magnetic heading) we needed to locate our final destination airport. I didn’t do that during my flight but should have. In other words, ifthe line was (flat) horizontal, our LOP heading would be 90 or 270 true east orwest depending on which side of SAME we thought we were. That would occur atexactly high noon.

Taking another look at the data charts.......
Check high noon at SAME, here http://aa.usno.navy.mil/data/docs/celnavtable.phpby entering S32° 50’ and W68° 50’ and for time enter 16:41 UT. Notice that the sun’s Zn=0°, at that exact time. If we were still flying we’d have a totally accurate latitude reading.

As a prelude to night flying and reading stars, and since we have this particulardata chart opened, notice that, if it were dark, we could read the star MIAPLACI Hc=+53 04.0 Zn=180.0 and get an exact latitude reading as well. And, if it were dark, we could read GIENAHwhich has a Zn=80.1° or RIGEL which has a Zn of 280.2° for an (almost) perfectly accurate longitude position at this particular time.


This was a time and distance measurementexercise where the info we gathered from our sun shots equated to lines (red,green, and blue) that crossed our path (that same o line on the chart) ...yeah?

I’m not exactly sure what you’re asking here, but I should point out the we didn’t need to use multiple lines for a single star reading. The multiple lineshowever are good for comparing the distances traveled between readings. I usedmultiple colored lines more as a reference and illustration more than necessity.


Why were shots taken at 60NM intervalsagain and should we always do it that way?

No particular reason. We can take as many readings as we want, at any interval, as long as we know what the reason for them is. Suppose you’d like to take readings 5 or 10 minutes apart just to get an idea of your rate speed for example. I believe the 60nm was to determine when we were 60nm out from SAME's LOP as a BOD (beginning of Descent) point. I believe, in subsequent flights, that I’ll allow more distance than 60nm to descend approximately 15,000’, depending on terrain of course. J


In this case we were using the Sextant to back up our figures we came up with by staying on course heading (as close as we could), keeping a constant ground speed (at cruise level) and keeping a close eye on time and distance with the clock ... is that about it?

Yes, in a sense you're right, but it's not all pilotage and wind correction angles. We can start a flight cold as long as we know where our NAVAIDS are when planning a flight. With the sextant, instead of NDB and/or VOR frequencies we use Fixed Points and airport latitudes and longitudes as NAVAIDS. Also, like VOR and NDB, intermittent "fixed points" should be spaced no farther than about 250nm. Instead of a VOR having a range of 195nm, our sextant readings have a readable range of 180nm. So yes, we make a flight plan, just as we would do any other. Perhaps we set in a frequency and wait for a gauge to come alive with VOR and NDB. When using the sextant we set in a coordinate and wait until the reading lines fall inside the 180nm mark on the graph. The only is we use the rate of speed formula two ways. One to find the rate of speed for a distance and time traveled. The other is to determining the time to the next point with a know GS (at cruise) and a set time. I have examples of the math problems in the demo flight.

In case you noticed my demo flight, using weather, was much faster than with no weather even though I’d checked the weather before TO and found a pure cross wind. It seems that sometime during the flight, the wind switched from cross to a tail wind and we averaged more than 200 knots GS between readings. This is proof that the sextant is a great tool for measuring GS. Another reason to take readings often is to determine if there’s a directional wind shifts as well as velocity changes. In fact, the sextant works as well as a DME for this purpose.

You nailed down the whole Moon thing very well and brought up some veryinteresting points on how it is rendered (or not) in MSFS.

Yeah. I knew something wasn't right between real Moon and FS Moon, but didn'thave a handle on it till now ... thanks!


Thank you Salt!


[BTW]

This puts me and Pedro in Mendoza ... yeah Pedro, he had to leave before thegringo's came back to find their plane broken, out of gas and a hundred miles southof where they left it ... and I needed a local guide until I get a grip on howto use the Sextant .... so things are working out for the three of us.

Me, Pedro and the ransom payment crate.

Great Job!!!! :salute:


PS Sorry about some words running togther. It seems to happen when copying from word.
I'd actually spent over an hour responding to the post, and when I was ready to post my login has expired. When I reloged the post didn't save and the screen was just blank.

 

[cputters]

Panel config works great, thanks

If I was to use my MAAM payware Dc, could I replace one of the windows with the window info you provided and it would work? (Add the guage number to the end of window00, then your info to the window I'll slot the sextant into.)

They use a full 10 windows, so I was thinking of replacing the co-pilot's window with the sextant.

 

[Dil52]

Sure Chris,

Just as you discribed, additional gauge number under window00 and slot for sextant.

Also

You don't need to replace any Icons. The ony reason for repalcing one is if you wanted to maintain the shift/number hot key for some reason. Personally I never use the hot keys, unless it's an addon of some kind.

Here's a pic of my MAAM R4D-6 panel using the sextant with an additional icon location.

View attachment 45465

The coordinates of the icon in the panel cfg are

gauge57=BB_sextant!icon2, 44,695,17,18

which put it in the right column, forth down (last) icon from the top.

I only have it in the pilot's window at this time.

Come to think of it, I should add an icon in the copilot's window as well. I'm getting tired of doing all the work while Carmen just sits over there looking pretty.

 

[cputters]

Nice. (I should be a pro at this modding business by the end of all this )

I'll have a go at this tonight.

Thanks again

 

[Dil52]

Read with interest Dil's info on moon phases in FS so I thought I'd take a look outside and then compare it to FSX. Must only be a couple days off because I can't really see any difference between the two, not that that's an exact measurement ( my eye calibration that is ). I was going to start using the sextant for moon shots during my first attempt at a classic era transatlantic flight so I'm glad it seems to be close to in phase.

Al

Hi Al,
You're right.

FSX is only about 58 or so hours out of sync at this time. The Full Moon forAugust, according to the USNO data charts, will officially start the 13th at 1857 UT. http://aa.usno.navy.mil/data/docs/MoonPhase.php

I checked FSX and the Full Moon starts on August 11th at 0800 UT
In MSFS there are 6 phases. They are New Moon, First Crescent, First Half, Full Moon, Last Half, Last Crescent. During the New Moon phase we only see a sliver of the moon, however it’s still observable for sextant purposes. The moon’s still there, it's just that all we can see is a sliver. J (FYI only….in the real world they actually use the sides of the moon for sextant readings due to the size of it).

You can check out a New Moon in FSX on August 27[SUP]th[/SUP] at 6:00AM EST or 10:00 UT in the mid to eastern part of (the eastern time zone) in the USA. After that, as you can see here, http://aa.usno.navy.mil/data/docs/RS_OneYear.php by setting in the Territory or Latitude and Longitude. The moon is going to begin syncing with the sun and will be up pretty much during daylight hours and not visable again until the middle of September. However it is visable after sunrise and before sunset at times.
Don't get confused by these examples. The moon is always visible at the times, except for a small differences each day, all around the earth when it's dark that is. Like the sun, comes up at 9:00PM in one time zone it comes up pretty much at 9PM in all time zones....jsut as the sun does.
The reason I used the USA as an example is that it's dark and visible when this particular Full Moon change occurs. You couldn't observe it in London because it is 0800 AM and too light.

Instead of slowly changing phases the moon snaps from one phase to the next. I'm guessing this usually happens on the top of an hour.
If you’d like to observe a moon "phase change" set the date to August 11, 0755 UT and fly anywhere in the USA from EDT to PDT. You will see it change at exactly 8:00 UT. If you set the time too close to the top of the hour, the scenery may already have changed it. That's why I suggested 7:55 instead of 7:59.

It is probably better to observe in a more western part of the USA, because it rises at 4:13AM local EST when it’s beginning to get daylight there. Of course in the PST zone it would only be 01:00AM local time.

August this year (2011) is a good time to use the moon for navigation since it’s out at night or “out of sync with the sun.” There are times when the moon is in sync with the sun or close to it, and not visible due to the brightness of the sun.

The improvement in FSX over FS9 is that you can see the New Moon as a thin sliver of a crescent.

It looks like the phases in FS9 are about 13 days out of sync at this time. The rise and set times are very accurate as always. If you don't see the moon when it's supposed to be coming up or be there it may be that the phase is in the New Moon.

dil

 

[oldpropfan]

Thanks for sharing all this info with us Dil, you have alot of knowledge about this sextant stuff and how to use it in FS.

Al

 

[cputters]

View attachment 45484

Can you please have a look over this? The sextant comes up only momentarily before disappearing.

I've checked it over and over but can't find the problem.

Thanks in advance.

 

[Dil52]

Hi Chris,

under "window titles" you have the sextant listed twice...that could be the problem

In case you earsed it, here's my MAAM C47 under windows titles.

[Window Titles]
Window00=Pilot Panel
Window01=Pilot IFR Panel
Window02=First Officer Panel
Window03=First Officer IFR Panel
Window04=Overhead Electrical Panel
Window05=Quadrant
Window06=Cowl Flaps
Window07=Flap and Gear Controls
Window08=GPS
Window09=Audio
Window10=Mini Panel
Window11=Sextant


dil

 

[robert41]

Very informative thread. One of these days, when I get some time, Iam going to have to make a long flight using only the sextant.

 

[cputters]

I give up.

Sorry guys.

I'll just stick it out in free flight for a little longer.

Thanks for all your help regardless.

 

[salt_air]

I give up.

Sorry guys.

I'll just stick it out in free flight for a little longer.

Thanks for all your help regardless.

Chris ... you can give out, but don't give up.


Suggestion ... have you flown the DC-3(s) that accompany the Radio Range Scenery?

Also are you in FSX or FS9? .... do you have FS9 installed?

 

[cputters]

Gday Salt,

You're right..I should have said "Give out!" lol. Mostly need a break from trying to get it going. I'll try again after a few few short legs of my RTW trip.

I'm in FSX/Accel

I'm not sure what DC's you mean. Where can I check them out? What will be the difference?

Thanks

 

[salt_air]

First off Chris they have all the sextant business in place on some very nice period specific panels.


Also you would want to use them because of how much better they handle and how they have been brought more in line with Douglas specs.


Another benefit is they are based off of the default DC-3 and that will afford you a bazillion paints and other free options.


I have five or six different DC-3's (favorite plane), but if I was held to just one that would be it.

To my knowledge the newest model should work in FSX (please mention if not) ... grab it here:http://www.flightsim.com/kdl.php?fid=152194

As I remember there's an installer so you'll have to direct the installation to a "new folder" ... just on the desktop.

After the unzip you should have 3 folders and an unistaller.

The three folders are aircraft, gauges, and sound.

Copy and paste the RR41 folder from inside the gauges folder into each of the panel folders (panel.1940 and panel.1945) in the DC3_RR41 folder inside the aircraft folder.

Then cut and paste the DC3_RR41 folder from inside the aircraft folder straight to your Sim Objects / Airplane folder.

Copy the DSD3 folder from inside the sound folder to your FSX root Sound folder.

Figure out which panel you like the best and then go after some paint jobs.




No GPS .... Try Plan G here:http://www.tasoftware.co.uk/planG.htm you may like it better than the GPS.

 

[cputters]

Legend!

I'll take a look later tonight. :ernae:

 

[cputters]

Ok. Finally got all the gear up at least.

My readings on the graph are all horizontal at zero though....any thoughts on that little number?

 

[Dil52]

Ok. Finally got all the gear up at least.

My readings on the graph are all horizontal at zero though....any thoughts on that little number?

Now that you have it all set up let's test it.

The readings will be zero if you have the coordinates set at your present location and take readings.



View attachment 45697

To illustrate: First, notice the coordinates of the aircraft highlighted in the red squared box.

Circled 1: I purposely added two degrees latitude and longitude to change the ASSUMED POSITION.

Circled 2: The first reading taken(the blue line) was with AZIMUTH set to 90° for a longitudinal reading.

The second reading taken (the green line) was with AZIMUTH set to 180° for a latitudinal reading.

(You can disregard the minus for 180. It just as well could be a plus 180) I always use plus for azimuth, this was an error on my part)

Also disregard the DISTANCE N. MILES (-125) in the illustration. That changed after creating the green line on the graph. The actual distances for latitude is 120nm and longitude is 100nm
One tap on the eyepiece will clear that number after creating the line.

This should get you going

 

[salt_air]

Quick Question(s)

Hope I'm not jumping the gun here Dil ... I'm sure some of this you will cover later, but the mortar is drying ... I need to put a few more cinder blocks in place while it's wet.




When taking Sun shots and Moon shots I notice once the coordinates are entered ... you just click the lens to start the shot and the target is right there in the lens.

Which of those data sheet (or Shift+Z) entries actually point the sextant at the target (Sun/Moon)?




(1) Does the Lat/Lon entries make the value of the little green circle on the chart next to the sextant?


(2) Then the Azimuth and Elevation values "point" the sextant at whatever you have chosen to shoot from the data sheets?






What about Stars? ... [Assuming the vast majority of us have no knowledge of the locations of constellations and especially the stars that make them up.]




Because there are (a lot) more than one we can use two or three (or more) in different parts of the sky to triangulate or get a fix ... awesome ... so to choose which of the Stars to use you should use ... which value on the data sheet should we use?


Then during the shot when we are trying to center the bubble in the up and down path of the target (Sun/Moon) we are actually fine tuning the numbers we entered off of the data sheet for accuracy .... like focusing a pair of binoculars, eh?





Hitting star 1 (or 2 or 3) on the chart beside the sextant throws a line (blue/green/red) down across the chart.

Is the little green circle in the middle of the chart always indicative of the plane's location?

How do we read what that line is telling us?





Probably should make a note (physically..hand written or whatever) of a few IF/THEN statements that could be memorized as a rule(s) of thumb ....

Like:

IF you're shooting at the airport prior to take off and/or pretty well know exactly (shift+Z) where you are and those coordinates have been entered ...

THEN then line that gets thrown down on the chart beside the sextant should pass through the center of the chart (little green circle) ... yeah?

 

[Dil52]

OK, I'm not a very fast typist, especially when trying to expalin things.

1) The illustration sample is merely a theoretical position showing an offsetof 2 degrees Lat/Lon from our location at SAME (the little green circle in the center of the graph). Yes, if we move the Lat/Lon back to -32 and -68 as we see by the Ctrl Z locations and take the readings the blue and green lines will intersect at the little green circle, our location.

Keep in mind we’re NOT really looking at any real star inthe FS sextant. This, as you may recall me saying earlier, is the big secret…Shhhhh
For reality purposes, we try to point the sextant in direction of the star we’re reading, but it’s not necessary. For instance, while heading south we can read a star in the north while the sextant is in the wind shield.

Having said that, it’s still important to know the azimuth and elevation of a star as it’s related to our ASSUMED POSITION for accurate readings. Lat and Lon are actual locations on earth. They don’t change and the data charts tell us, by setting the correct time and location of ASSUMEDPOSITION at the USNO site.

The result is the Zenith of each readable star at that exact moment in time. The Zenith (not to be confused with Zn (azimuth) is where a star is, if we drew a line straight down to earth, from it at that moment in time. Also, as we revolve around during the course of a year the same constellations are not always visible at the same times. We always can see Polaris in the northern hemisphere, but it moves very little.

Side note:
I was explaining the movement of stars and the moon at an exact time to some friends, last night, as we were watching the moon rise just before sunset. I was saying, if the moon was only a few thousand feet above the earth, and was stationary as it is, that we’d see it go overhead at about 1000 MPH. The look on their faces was something to behold.

This, of course, is a well known fact, but when put in that perspective most people don’t think of it that way. PS: I didn't explain to them how I know this. I gave up trying to explain to people, about my FS hobby, years ago.

2) Also, the star shots are only theoretical for the illustration. It's rare if we would ever see a star located exactly at an even 0, 90, 180, or 270 degrees on the data charts. If our location was exactly at the Equator during either Equinox, the sun would rise at 90 and set at 270 degrees. In the north we like Polaris (the north star) because it's location is very close to 0 or 360 degrees for a great latitude readings all year.
In the south, by the time we reach a Lat of S40, ACRUX will begin to be our usual latitude (southern) star. ACRUX, the A (Alpha) star in the Southern Cross, is not as good as Polaris, but is still the star of choice, for latitude readings, as it’s near a Zn (azimuth) of 180 degrees.

What about Stars? ... [Assuming the vast majority of us have no knowledge of the locations of constellations and especially the starsthat make them up.]

As I said, all we need to know is what’s on the data charts. As long as we set the Zn and Hc of a star we’ll get a good reading no matter where the FS sextant is pointing. If we were reading a real sextant we’d need to point it at the exact star to get our reading. Then is when we'd need to know the constalation. Keep in mind the data chart tell you where the start is at a any given time that you read the result of GET DATA.
Suppose the star's Zn was 90 degrees and the Hc was +15 degrees. We'd look toward due east and 15 degrees above the horizon.
It would probably be the brightest star since those are the ones listed on the charts.

Because there are (a lot) more than one we can use two or three (or more) indifferent parts of the sky to triangulate or get a fix ... awesome ... so tochoose which of the Stars to use you should use ... which value on the datasheet should we use?

Use the values under Zn for azimuth and the values under Hc for elevation (set in by adjustingthe course and fine wheels to the right of the eye piece) before taking the reading)Notice, that when we’re taking a reading AT our location, the bubble is centerand we don’t need to adjust the fine adjustment. If the ASSUMED POSITION is different than our location we need to center the bubble in the circle I usethe biggest one (#3) gotten by adjusting the wheel on the left side of the eyepiece.

Then during the shot when we are trying to center the bubble in the up and down path of the target (Sun/Moon) we are actually fine tuning the numbers weentered off of the data sheet for accuracy .... like focusing a pair ofbinoculars, eh?
Yes
Hitting star 1 (or 2 or 3) on the chartbeside the sextant throws a line (blue/green/red) down across the chart.

Is the little green circle in the middle of the chart always indicative of theplane's location?
Yes, The center of the chart is always our location

How do we read what that line is telling us?
If we’re reading a star with a Zn (azimuth) of near east or west then we are reading the distance to a LOP or (point), in longitude that we want to reach. That would be where the line crossed the horizontal line left or right of the little green dot.

If we’re reading a start near a Zn (azimuth) of near north or south then we’re reading a distance to the latitude we want to reach. That would be where the line crossed the verticle line above and below of the little green dot.

Notice that each line on the graph represents 60nm.

Edit:Hitting star 1 (or 2 or 3) on the chartbeside the sextant throws a line (blue/green/red) down across the chart.

We can move the little green circle, located in the center of the chart, by hitting the green arrows hot spots located on the bottom and left side of the graph. If we center the little green circle to where the 2 or 3 of the star readings cross we can then read the heading and distance (from that ASSUMED POSITION) to our aircraft by clicking on the NM hot spot located in the lower left side of the graph. We'd need to fly the reciprocal (180 degrees) of that heading to reach that location.
Keep in mind, when navigating at night, that with two or more good Lat/Lon stars readings, we don't need to find a LOP on one side of our destination airport then fly that LOP to locate our airport. With two good reading, when the lines cross in the center of the graph, we're right at our destination. Just look down.

Also, when flying during the day, we'd fly the best LOP. That is to say, if the Sun was in the east or west the line would be vertical and we'd fly north or south direction to match the angle of the reading line to locate our destination airport. Conversely, if the reading was taken near noon our, latitude LOP would be or accurate and we'd fly a direction of east or west to locate our airport. If the line crossed the little green dot at a 45 degree angle we'd fly northeast, southeast, northwest or southwest to locate the destination depending on the angle of the line. That may be foggy now, but once you understand what the lines are telling us it'll be clearer. For now, don't worry about it too much if it isn't clear.




Probably should make a note(physically..hand written or whatever) of a few IF/THEN statements that couldbe memorized as a rule(s) of thumb ....

IF you're shooting at the airport prior to take off and/or pretty well knowexactly (shift+Z) where you are and those coordinates have been entered ...

THEN then line that gets thrown down on the chart beside the sextant should pass through the center of the chart (little green circle) ... yeah?

Yeah

We can try to make a step by step list at this point. Yougive it a go, and I’ll do the same and we’ll compare notes.

dil

Here's quick a quiz: Notice, when looking at the illustration of the sextant in the post above, that we moved the Lat and Lon 2 degrees each from our location at SAME.
Why is the blue line only 100nm and the green line 120nm from our present location?